Optical disc having buffering areas capable of storing a pattern for obtaining tracking error signals and recording and/or reproducing apparatus therefor

ABSTRACT

At the boundary between the program area and the recording area, buffering areas where no valid data exists are respectively provided in the program area and the recording area. These respective buffering areas are caused to be access inhibit area, and neither recording or reproduction is carried out in these areas. For this reason, oscillation of the tracking servo which is likely to take place when light spot is passed through the boundary between the program area and the recording area is suppressed to realize tracking servo stable at all times. Thus, temporary missing of information signals is prevented.

TECHNICAL FIELD

This invention relates to an optical disc such as a magneto-opticaldisc, etc., and more particularly to an optical disc including arecording area and a program area (premastered area) within the discsurface and a recording and/or reproducing apparatus for such opticaldisc.

BACKGROUND ART

In order to cope with requirements of miniaturization and/or highdensity recording with respect to magneto-optical disc in recent years,so called hybrid media each including a recording area and a programarea (premastered area) within a single disc surface have been devisedat present.

In such hybrid media, the program area is comprised of emboss pits, andthe recording area is comprised of wide grooves. At the innermostcircumferential portion of each of the hybrid media, lead-in area whereTOC information corresponding to table of contents of recordedinformation is recorded is provided.

The configuration of such hybrid media is adopted in variousmagneto-optical discs.

Meanwhile, in the magneto-optical disc, the three-beam method isemployed as a method of obtaining tracking error signal thereof.

As shown in FIGS. 1 to 3, this three-beam method is a method in whichmain beam spot B for reading signal and sub-beam spots A, C spaced by apredetermined distance in track width direction before and after themain beam spot B are used to obtain a tracking error signal. In thethree-beam method, the state where the main beam spot B is directlyabove the track T as shown in FIG. 1 is the most preferable state. Inthis state, areas of the portions where the sub-beam spots A, C cross(are laid across) the track T are the same, resulting in output of 0.Moreover, when the main beam spot B deviates (is shifted) slightly tothe left side as shown in FIG. 2, the area of the portion where thesub-beam spot C crosses (is laid across) the track T is greater thanthat of the sub-beam spot A, resulting in output of positive value.Further, when the main beam spot B deviates (is shifted) slightly to theright side as shown in FIG. 3, the area of the portion where thesub-beam spot A crosses (is laid across) the track T is greater thanthat of the sub-beam spot C, resulting in output of negative value. Inthis way, track deviation of the main beam spot B is detected. Thus,correction is implemented in dependency upon output value correspondingthereto.

However, in the case of obtaining a tracking error signal of the hybridmedia by the three-beam method, since, in the hybrid media, as describedabove, the program area is comprised of emboss pits and the recordingarea is comprised of wide grooves on the disc surface thereof, there isthe possibility that phase of the tracking error signal is changed by180 degrees (rotated) when light spot is passed through the boundarybetween the program area and the recording area. Accordingly, greatacceleration is applied to the optical pick-up at this time, so anobject lens (objective) is vibrated in the inner circumferentialdirection or in the outer circumferential direction by inertia. For thisreason, the tracking servo may be in oscillated state. In addition, suchvibration would affect the focus servo as well. As a result, response ofthe focus servo is lowered. Thus, there may take place the worst statewhere the entirety of the system is stopped. In this case, for recovery(restoration), a certain time is required. When viewed from end user,missing of information would temporarily take place.

Moreover, in the optical disc, so called CLV system is ordinarilyemployed. For this reason, a rotation synchronizing signal of theoptical disc is taken out from signals recorded on the optical disc tocontrol the number of rotations of the spindle (motor) so that therotation synchronizing signal has a fixed period. This rotationsynchronizing signal is ordinarily obtained from Eight to FourteenModulation (hereinafter simply referred to as EFM) signal or Address InPregroove (hereinafter simply referred to as ADIP) signal. However,since EFM signal does not exist at the innermost circumferential portionof the recording area of the hybrid media, there are instances wherewhen light spot enters the recording area, the number of disc rotationsis not stabilized even in the state where the tracking servo is stable.

This invention has be proposed in view of actual circumstances asdescribed above, and its object is to provide an optical disc adaptedfor implementation of such a control to suppress oscillation of thetracking servo which is apt to take place when light spot is passedthrough the boundary between the program area and the recording area torealize tracking servo stable at all times to prevent temporal missingof information, and to stabilize the number of disc rotations at alltimes, and a recording and/or reproducing apparatus for such opticaldisc.

DISCLOSURE OF THE INVENTION

An optical disc according to this invention comprises, within a discsurface, a first recording area where data using physical unevenportions are recorded in advance, a second recording area where groovesare formed, and buffering areas where no valid data exists disposedwithin the respective first and second areas between the first and thesecond recording areas. Since access is inhibited in such bufferingregion (areas), both recording and reproduction are not carried out.

Further, an optical disc according to this invention comprises a firstrecording area where data are recorded by phase pits, a second recordingarea where grooves are formed and adapted so that data are permitted tobe recorded, and a buffering area provided between the first recordingarea and the second recording area, wherein data are recorded, inpredetermined recording units, in the first recording area and thesecond recording area, and only a pattern for generating tracking errorsignal is formed in the buffering area.

In this case, the buffering area is an area having a size of multiple ofinteger of the predetermined recording unit or more. For example, whenthe predetermined recording unit is assumed to be 1 cluster consistingof 36 sectors each having or consisting of 2352 bytes, it is desirablethat the buffering area is 2 clusters or more. At the innercircumferential portion on the disc surface, 2 clusters correspond tosubstantially 10 tracks, and further correspond to substantially 16 μmin terms of the track width.

In this case, it is preferable that linking sectors for de-interleavingof 2 sectors or more are provided after the last cluster where the lastinformation is recorded of the first recording area. This is carried inconsideration of the case where interleaving length in the optical discis longer than 1 sector of the data format. By providing linking sectorsafter the last cluster, missing of information is prevented.

Further, a recording and/or reproducing apparatus according to thisinvention is directed to a recording and/or reproducing apparatus for anoptical disc as described above including a first recording area wheredata are recorded in advance by physical uneven portions, a secondrecording area where grooves are formed, and a buffering area whereaccess is inhibited, which is provided between the first and secondrecording areas, wherein the apparatus comprises: an optical head forreading out data from the optical disc, tracking error signal generatingmeans for generating a tracking error signal on the basis of an outputsignal from the optical head, tracking control means for carrying outtracking control on the basis of the tracking error signal generated bythe tracking error signal generating means, amplitude detecting meansfor detecting amplitude of the tracking error signal generated by thetracking error signal generating means, and control means forcontrolling the tracking control means on the basis of a detectionsignal from the amplitude detecting means, whereby the control means isoperative to carry out switching of polarity (direction in control) ofthe tracking control means in dependency upon whether the optical headscans either the first recording area or the second recording area ofthe optical disc, and to move the optical head in a radial direction ofthe optical disc in the state where tracking control operation by thetracking control means is turned OFF thereafter to allow the trackingcontrol means to be operative when detection result from the amplitudedetecting means indicates that amplitude of the tracking error signalfrom the tracking error signal generating means falls within apredetermined range.

Further, a recording and/or reproducing apparatus according to thisinvention is directed to a recording and/or reproducing apparatus for anoptical disc including a first recording area where data using physicaluneven portions are recorded in advance, a second recording area wheregrooves are formed, a buffering area provided between the firstrecording area and the second recording area, and a management area inwhich management data for carrying out management of data recorded inthe first and second recording areas is recorded, wherein the apparatuscomprises an optical head for reading out data from the optical disc,and control means for controlling movement operation of the optical headon the basis of the management data which has been read out from theoptical head, whereby the control means is operative so that when theoptical head moves from any one of the first and second recording areasof the optical disc to the other recording area, it inhibits access tothe buffering area of the optical disc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a model view showing the state where no tracking error takesplace when the three-beam method is used.

FIG. 2 is a model view showing the state where main beam spot B isslightly shifted to the left side.

FIG. 3 is a model view showing the state where main beam spot B isslightly shifted to the right side.

FIG. 4 is a plan view showing, in a model form, a magneto-optical discwhich is an embodiment of an optical disc according to this invention.

FIG. 5 is a model view showing data format of the magneto-optical discof the embodiment.

FIG. 6 is a block diagram showing outline of a magneto-optical discrecording/reproducing apparatus which is an embodiment of a recordingand/or reproducing apparatus according to this invention.

FIG. 7 is an exploded perspective view showing the configuration ofoptical head of the magneto-optical disc recording/reproducingapparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

Best mode for carrying out an optical disc according to this inventionwill now be described with reference to the attached drawings. This bestmode is directed to a magneto-optical disc so called hybrid media eachincluding, within a single disc surface, a recording area and a programarea (premastered area).

On the magneto-optical disc, as shown in FIG. 4, there is provided alead-in area 1 where TOC information corresponding to table of contentsof information recorded at the innermost circumferential portion on thedisc surface is recorded. At the outer circumferential portion of thelead-in area 1, a program area (premastered area) 2 is provided.Further, at the outer circumferential portion of the program area 2, arecording area 3 which is a recordable area is provided. The programarea 2 is caused to be emboss pits, and the recording area 3 is causedto be wide grooves. Particularly, at the boundary between the programarea 2 and the recording area 3, buffering area 4, 5 where no valid dataexists are respectively provided in the program area 2 and the recordingarea 3. These respective buffering areas 4, 5 are an access inhibitarea, and neither recording nor reproduction is carried out in theseareas. Particularly, only pattern for generating tracking error signalis formed. In more practical sense, pattern for generating trackingerror signal having the same polarity as polarity of tracking errorsignal generated in the program area 2 is formed by emboss pits withinthe buffering area 4. In addition, pattern for generating tracking errorsignal having the same polarity as polarity of tracking error signalgenerated in the recording area 3 is formed by grooves within thebuffering area 5.

In this case, in more practical sense, it is desirable that therespective buffering areas of the recording area and the program arearespectively have the range of 2 clusters or more. In this case, twoclusters correspond to substantially 10 tracks on the disc surface, andfurther correspond to substantially 16 μm in terms of the track width.

Further, it is preferable to provide linking sectors for de-interleavingof 2 sectors or more after the last cluster where last information isrecorded of the program area. This is carried out in consideration ofthe case where interleaving length in the optical disc is longer thanone sector of the data format. By providing linking sectors after thelast cluster, missing of information is prevented.

More practical data format of the magneto-optical disc will now bedescribed. In this data format, as shown in FIG. 5, recording is carriedout with 36 sectors each having or consisting of 2352 bytes being as onecluster (one block). In this case, three sectors arranged (allocated) atthe leading portion are used as linking sector L.

In the magneto-optical disc, in the case where Advanced Cross InterleaveReed-Solomon Code (ACIRC) is employed as interleaving therefor, thisinterleaving length is 108 frames. However, when one sector of themagneto-optical disc is, e.g., 98 frames, it is necessary to providelinking sectors of 108 frames or more before and after data is writtenonto such disc in order to complete error correction. Namely, ifinformation of 5 sectors in total of respective 2 sectors before andafter and own 1 sector exist at the minimum in order to read out onesector, reproduction cannot be carried out. Accordingly, it is necessaryto provide linking sectors for de-interleaving of 2 sectors or moreafter the last cluster where last information is recorded of the programarea 2.

In this embodiment, since 4 sectors of 36 sectors of one cluster areused for linking sectors L and sub sector S, recording of information iscarried out such that writing is started from the middle portion of thesecond linking sector L, and error correction is completed by using upto the portion in the middle of the second sector of the linking sectorsL positioned at the leading portion of the next cluster with respect tothe last protruded portion. It is to be noted that, in the reproductiononly optical disc, the linking sectors L are used for sub data.

The remaining 32 sectors of 36 sectors of one cluster consist ofcompressed audio data, and bytes for data of 2352 bytes of one sectorare 2332 bytes. One unit consisting of 424 bytes of compressed audiodata is called one sound group. In this embodiment, rates of the soundgroups are caused to be in correspondence with each other in such amanner that 11 sound groups are caused to correspond to 2 sectors, andthe remaining respective one sound groups are sequentially transmittedand processed. Namely, in the first one sector, left and rightchannels×5 sound groups and left channel of the sixth sound group arerecorded, and left and right channels of 5 sound groups are recordedsubsequently to the right channel of one sound group are then recorded.

It is to be noted that when compression of one sound group is released,information corresponding to 11.62 m sec. of 512 samples of the left andright channels is provided.

In the above-mentioned magneto-optical disc, at the boundary between theprogram area 2 and the recording area 3, buffering areas 4, 5 where novalid data exists are respectively provided in the program area 2 andthe recording area 3. Namely, even in the case where inversion takesplace in phase of the tracking error signal when the optical pick-up ispassed through the boundary between the program area 2 and the recordingarea 3, there is no possibility that sudden phase inversion may takeplace because light spot moves from the program area 2 to the recordingarea 3 through the respective buffer areas 4, 5. Accordingly,oscillation of the tracking servo which is apt to take place in hybridmedia is suppressed. Thus, stable tracking error signal can be obtainedat all times.

Moreover, since buffer areas 4, 5 exist when light spot moves from theprogram area 2 to the recording area 3, the number of disc rotations canbe stabilized.

Namely, in accordance with the optical disc according to this invention,oscillation of the tracking servo which is apt to take place when lightspot is passed through the boundary between the program area and therecording area is suppressed to realize stable tracking servo at alltimes. Thus, temporary missing of information can be prevented and thenumber of disc rotations can be stabilized.

The best mode for carrying out a recording and/or reproducing apparatusaccording to this invention will now be described with reference to theattached drawings. This best mode is directed to a magneto-optical discrecording/reproducing apparatus 10 as shown in FIG. 6 adapted forimplementing recording and/or reproducing processing to theabove-described magneto-optical disc shown in FIG. 4, i.e.,magneto-optical disc provided with program area 2 where data arerecorded in advance by emboss pits which are physical uneven portions,recording area 3 where grooves are formed, and buffering areas 4, 5provided between the program area 2 and the recording area 3 and adaptedso that access is inhibited.

This magneto-optical disc recording/reproducing apparatus 10 comprisesan optical head 18 for reading out data from magneto-optical disc 6, atracking error signal generating circuit 30 for generating a trackingerror signal on the basis of an output signal from the optical head 18,a servo processing circuit 26 for driving, in radial direction r of themagneto-optical disc 6, by a bi-axial actuator 19, object lens whichwill be described later of the optical head 18 on the basis of thetracking error signal generated by the tracking error signal generatingcircuit 30, a level discriminating circuit 31 for detecting level of thetracking error signal generated by the tracking error signal generatingcircuit 30, and a system controller 32 for controlling the servoprocessing circuit 26 on the basis of a detection signal from the leveldiscriminating circuit 31.

This magneto-optical disc recording/reproducing apparatus 10 implementsrecording and/or reproduction processing to data of the magneto-opticaldisc 6 rotationally driven by a spindle motor 27. At the time ofrecording data with respect to the magneto-optical disc 6, thisapparatus applies, by a magnetic head 17, modulation magnetic fieldcorresponding to recording data in the state where laser beams areirradiated onto the magneto-optical disc 6 by the optical head 18 tothereby carry out so called magnetic field modulation recording torecord data into grooves of the recording area 3 of the magneto-opticaldisc 6. On the other hand, at the time of reproduction, this apparatustraces grooves of the magneto-optical disc 6 by laser beams by using theoptical head 18 to carry out reproduction.

In this embodiment, the optical head 18 is of a structure as shown inFIG. 7. When the case where a magneto-optical signal is read out fromthe recording area 3 of the magneto-optical disc 6 is taken as anexample, laser beams emitted from a laser diode 41 serving as a lightsource are caused to be three beams by a grating 42. These three beamsare caused to be parallel beams by a collimator lens 43, and are thenincident to a beam splitter 44. The beam splitter 44 allows the laserbeams to be transmitted therethrough. The parallel laser beams whichhave been transmitted through the beam splitter 44 are caused to undergochange of traveling direction (optical path) by 90 degrees by a risingmirror 45, and are reached to object lens 46. The object lens 46converges the parallel laser beams to irradiate them into the recordingarea 3 of the magneto-optical disc 6.

Reflected laser beams from the recording area 3 on the magneto-opticaldisc 6 are caused to be parallel beams for a second time by the objectlens 46, and are reflected by the beam splitter 44. The reflected lightthus obtained is guided to a photodetector 50 which is light detectorthrough a Wollaston prism 47, a collimator lens 48 and a multi-lens 49.

The optical head 18 is provided at the position opposite to the magnetichead 17 through the magneto-optical disc 6. In the case of writing dataonto the magneto-optical disc 6, the magnetic head 17 is driven by amagnetic head drive circuit 16 to apply modulation magnetic headcorresponding to recording data, and to irradiate laser beams onto thetarget track of the recording area 3 of the magneto-optical disc 6 bythe optical head 18 to thereby record data by the magnetic fieldmodulation system. Moreover, this optical head 18 detects reflectedlight of laser beams irradiated onto the target track by using thephotodetector 50 to deliver it to a focus error signal generatingcircuit 29 and the tracking error signal generating circuit 30.

Further, in the case of reproducing data from the magneto-optical disc6, the optical head 18 delivers a detection signal detected at thephotodetector 50 to the focus error signal generating circuit 29 and thetracking error signal generating means 30, and detects differencesbetween light quantities and polarization angles (Kerr rotationalangles) of rays of reflected light from the program area 2 and therecording area of the laser beams to generate reproduction signals.

Namely, this magneto-optical disc recording/reproducing apparatus 10converges laser beams for reproduction and writing, which are outputtedfrom the laser diode 41 serving as light source of the optical head 18,and are caused to be through optical elements such as grating 42,collimator lens 43, beam splitter 44, etc. into the program area 2 andthe recording area 3 of the magneto-optical disc 6 through the objectlens 46 of which focus direction and tracking direction are subjected todrive control by the bi-axial actuator 19.

In the case of recording data onto the magneto-optical disc 6, themagneto-optical disc recording/reproducing apparatus 10 drives the laserdiode 41 through a LD driving circuit 20 by control of the systemcontroller 32 to allow the laser diode 41 to emit high output laserbeams for writing therefrom. The writing high output laser beams emittedfrom the laser diode 41 are irradiated onto the target track of therecording area 3 of the magneto-optical disc 6 by the object lens 46 ofwhich focus direction and track direction are driven and controlled bythe bi-axial actuator 19. At the back side of the target track of therecording area 3 of the magneto-optical disc 6 onto which the writinglaser beams have been irradiated, the magnetic head 17 is positioned.The magnetic head 17 is driven by the magnetic head drive circuit 16 torecord recording data obtained by modulating information signal at theposition where the writing laser beams have been irradiated. Themagnetic head drive circuit 16 receives modulated data for recordingfrom an encoder 15 for modulation. The modulation encoder 15 adds, e.g.,error correction code by the ACIR system to compressed data compressedat an encoder 12 for compression to modulate it by the Eight to FourteenModulation (EFM) system thereafter to deliver it to the magnetic headdrive circuit 16. In this case, error correction of the ACIR system is asystem of apply Add-on Interleave (processing) only to data with respectto CIR to implement sequencing to data on the disc so that they are inorder of real times to interleave only parity of error correction. Forthis reason, modulation magnetic filed corresponding to EFM recordingdata is recorded into the target track to which high output laser beamsare irradiated from the optical head 18 of the recording area 3 of themagnet-optical disc 6 by the magnetic head 17.

On the other hand, in the case of reproducing data from themagneto-optical disc 6, the magneto-optical disc recording/reproducingapparatus 10 drives the laser diode 41 through the LD drive circuit 20by control of the system controller 32 to allow the laser diode 41 toemit lower output laser beams for reproduction therefrom. The loweroutput laser beams for reproduction which have been emitted from thelaser diode 41 are irradiated onto the target track of the program area2 and the recording area 3 of the magneto-optical disc 6 by the objectlens 46 of which focus direction and the track direction are driven andcontrolled by the bi-axial actuator 19. Reflected laser beams from theprogram area 2 and the recording area 3 of the magneto-optical disc 6are guided to the photodetector 50 which is the light detector withinthe optical head 18, and are irradiated thereonto.

A portion of reproduction signal obtained at the photodetector 50 iscaused to be RF signal by a RF amplifier 21 and is delivered to anaddress decoder 22, a decoder 23 for demodulation and the servoprocessing circuit 26.

The address decoder 22 demodulates cluster, sector address informationcalled, e.g., ADIP (Address In Pregroove) signal from the RF signal todeliver it to the encoder 15 for modulation.

The decoder 23 for demodulation implements error correction processingof the ACIRC system and the EFM data demodulation processing to the RFdata.

The servo processing circuit 26 controls the spindle motor 27 forrotationally driving the magneto-optical disc 6 in accordance with theRF signal. Moreover, the servo processing circuit 26 controls a feedmotor 28 in accordance with the RF signal to move the optical head 18and magnetic head 17 to the target track position of the magneto-opticaldisc 6. This servo processing circuit 26 is also supplied with focuserror signal and tracking error signal from the focus error signalgenerating circuit 29 and the tracking error signal generating circuit30.

In this case, demodulated data from the decoder 23 for demodulation isoutputted to a decoder 24 for expansion while being stored into anexternal RAM 14 by control of a memory controller 13. For example, inthe case where 1M bit DRAM is used as the external RAM 14, datacorresponding to about 3 sec. can be stored. Thus, even in the casewhere reproduction data from the magneto-optical disc 6 is interruptedby vibration, etc., such reproduction data can be compensated by datastored in the external RAM 14. Thus, sound jump for a time period untilcorrect data is reproduced can be prevented. The decoder 24 forexpansion expands the data which has been read out from the external RAM14 by control of the memory controller 13 to output it from an outputterminal 25.

The remaining portion of the reproduction signal which has been obtainedat the photodetector 50 is delivered to the focus error signal detectingcircuit 29 and the tracking error signal detecting circuit 30. A focuserror signal and a tracking error signal that the focus error signaldetecting circuit 29 and the tracking error signal detecting circuit 30have respectively detected are delivered to the servo processing circuit26. The servo processing circuit 26 delivers a focus servo signal and atracking servo signal to the bi-axial actuator 19 in accordance with thefocus error signal and the tracking error signal to drive the objectlens 46 in the focus direction and in the track direction.

In this case, the tracking error signal obtained at the tracking errorsignal detecting circuit 30 is also delivered to the leveldiscriminating circuit 31 in addition to the servo processing circuit26.

The level discriminating circuit 31 informs the system controller 32 asto whether or not the optical head 18 scans the program area 2 or therecording area 3 at present by detecting level of the tracking errorsignal in the respective areas. Level of the tracking error signal inthe program area 2 where emboss pits are formed and that in therecording area 3 where grooves are formed are different. The level ofthe tracking error signal of the recording area 3 is about twice graterthan the level of the tracking error signal of the program area 2.Accordingly, the level discriminating circuit 31 is operative so that inthe case where it discriminates that current tracking error signal isthe tracking error signal of the program area 2, it outputs signal ofLOW level to the system controller 32. In contrast, the leveldiscriminating circuit 31 is operative so that in the case where itdiscriminates that current tracking error signal is the tracking errorsignal of the recording area 3, it outputs a signal of HIGH level to thesystem controller 32.

The system controller 32 can judge, by change in the signal of LOWlevel, or HIGH level delivered from the level discriminating circuit 31,whether the optical head 18 moves from the inner circumference to theouter circumference of the magneto-optical disc 6, or moves from theouter circumference to the inner circumference thereof. Namely, if thesignal changes from LOW level to HIGH level, it can be judged that theoptical head 18 moves from the inner circumference to the outercircumference. In contrast, if the signal changes from HIGH level to LOWlevel, it can be judged that the optical head 18 moves from the outercircumference to the inner circumference.

Moreover, the system controller 32 switches, in dependency upon whetherthe optical head 18 scans either the program area 2 or the recordingarea 3 of the magneto-optical disc 6, polarity (direction) of thetracking control that the servo processing circuit 26 carries out. Thisis to cope with the case where when the optical pick-up 18 is passedthrough the boundary between the program area 2 and the recording area3, inversion takes place in the phase of the tracking error signal.

The system controller 32 allows the tracking control operation at theservo processing circuit 26 to be turned OFF thereafter to move theoptical head 18 in the radial direction r of the magneto-optical disc 6.Further, when the level discriminating circuit 31 discriminates thatlevel of the tracking error signal falls within a predetermined range,the system controller 32 allows the servo processing circuit 26 to carryout the tracking control.

Namely, the system controller 32 is operative so that in the case whereit judges from level discrimination result of the level discriminatingcircuit 31 that the optical head 18 scans the program area 2 and therecording area 3 at present, it allows the servo processing circuit 26to carry out tracking control operation.

Moreover, the system controller 32 is operative so that it judges fromlevel discrimination result of the level discriminating circuit 31 thatthe optical head 18 does not scan the program area 2 and the recordingarea 3 at present, it controls drive of the feed motor 28 through theservo processing circuit 26 to move scanning point of the optical head18 in the radial direction r.

In this case, consideration is made in connection with the case where,as the magneto-optical disc 6, there is used magneto-optical discprovided with a management area for recording management data whichcarries out management of data recorded in the program area 2 and therecording area 3 in addition to the program area 2, the recording area 3and buffering areas 4, 5. In this case, the system controller 32 isoperative so that when the optical head 18 moves from any one of theprogram area 2 and the recording area 3 of the magneto-optical disc 6 tothe other area, it inhibits access to the buffering areas 4, 5 of themagneto-optical disc 6. Moreover, the system controller 32 stops, in thebuffering areas 4, 5, tracking control at the servo processing circuit26 on the basis of management data which has been read out from themagneto-optical disc 6.

Moreover, a key input operation section 33 and a display section 34 areconnected to the system controller 32. This system controller 32 carriesout control of the recording system and the reproducing system in theoperation mode designated by operation input information by the keyinput operation section 33. Further, the system controller 32 allows thedisplay section 34 to display bit compression mode on the basis of bitcompression mode information at the encoder 12 for compression which hasbeen caused to undergo selective switching by the key input operationsection 33, or bit compression mode information within reproduction dataobtained through the reproducing system from the RF amplifier 21, anddisplays reproduction time on the display section 34 on the basis ofdata compression rate in the bit compression mode and reproductionposition information on the recording track.

As described above, in accordance with the magneto-optical discrecording/reproducing apparatus 10, even in the case where inversiontakes place in the phase of the tracking error signal when the opticalpick-up 18 is passed through the boundary between the program area 2 andthe recording area 3, polarity (direction) of the tracking control ofthe servo processing circuit 26 is switched by the level discriminatingcircuit 31 and the system controller 32. Further, when the optical head18 is caused to be accessed, tracking servo is carried out after levelof the tracking error signal is discriminated without allowing the servoprocessing circuit 26 to immediately start tracking control.Accordingly, oscillation can be suppressed. In addition, withoutaccessing the optical pick-up 18 thereafter to allow the servoprocessing circuit 26 to immediately complete the tracking control,tracking control is completed after the level of the tracking errorsignal becomes steady (stable). Accordingly, oscillation can besuppressed.

Namely, in accordance with the recording and/or reproducing apparatusaccording to this invention, since oscillation of the tracking servo canbe suppressed, stable tracking can be realized at all times, andtemporal missing of information signal can be prevented.

What is claimed is:
 1. An optical disc including:a first recording areawhere data using physical uneven portions are recorded in advance; asecond recording area where grooves are formed; and a buffering areaprovided between the first recording area and the second recording area,wherein only a pattern for generating a tracking error signal is formedin the buffering area.
 2. An optical disc as set forth in claim1,wherein the buffering area is formed by physical uneven portions. 3.An optical disc as set forth in claim 1,wherein the buffering area iscomposed of a first buffering area formed by physical uneven portions,and a second buffering area where grooves are formed.
 4. An optical discincluding:a first recording area where data using phase pits arerecorded in advance; a second recording area where a plurality ofgrooves are formed and adapted so that said grooves are suitable forrecording data therewithin; and a buffering area provided between thefirst recording area and the second recording area,wherein data arerecorded, in predetermined recording units, in the first and secondrecording areas, and only a pattern for generating a tracking errorsignal is formed in the buffering area.
 5. An optical disc as set forthin claim 4,wherein a pattern for generating a tracking error signalhaving the same polarity as polarity of a tracking error signalgenerated in the first recording area and a pattern for generating atracking error signal having the same polarity as polarity of a trackingerror signal generated in the second area are formed in the bufferingarea.
 6. An optical disc as set forth in claim 4,wherein the bufferingarea is comprised of an area formed physical uneven portions.
 7. Anoptical disc as set forth in claim 4,wherein the buffering area iscomposed of a first buffering area formed by using physical unevenportions, and a second buffering area where grooves are formed.
 8. Anoptical disc as set forth in claim 4,wherein the buffering area is anarea having size of at least a multiple of integer of the predeterminedrecording unit.
 9. An optical disc as set forth in claim 4,wherein thepredetermined recording unit consists of plural linking sectors andplural data sectors where data are recorded, linking sectors of at least2 sectors being provided after the last recording point of the firstrecording area.
 10. A recording and/or reproducing apparatus for anoptical disc including a first recording area where data are recorded inadvance by physical uneven portions, a second recording area wheregrooves are formed, and a buffering area provided between the first andsecond recording areas and adapted so that access is inhibitedtherewithin,the apparatus comprising: an optical head for reading outdata from the optical disc; tracking error signal generating means forgenerating a tracking error signal on the basis of an output signal fromthe optical head; tracking control means for carrying out trackingcontrol on the basis of the tracking error signal generated by thetracking error signal generating means; amplitude detecting means fordetecting amplitude of the tracking error signal generated by thetracking error signal generating means; and control means forcontrolling the tracking control means on the basis of a detectionsignal from the amplitude detecting means,whereby the control means isoperative to switch polarity (direction in control) of the trackingcontrol means in dependency upon whether the optical head scans eitherthe first recording area or the second recording area, and to move theoptical head in a radial direction of the optical disc in the statewhere tracking control operation by the tracking control means is turnedoff thereafter to allow the tracking control means to be operative whendetection result from the amplitude detecting means indicates thatamplitude of the tracking error signal from the tracking error signalgenerating means falls within a predetermined range.
 11. A recordingand/or reproducing apparatus as set forth in claim 10,wherein thecontrol means is operative so that when detection result by theamplitude detecting means indicates that amplitude of the tracking errorsignal from the tracking error signal generating means is levelsubstantially equal to level of a tracking error signal of either thefirst recording area or the second recording area, it switches thetracking control means so that the tracking control means is placed inoperative state.
 12. A recording and/or reproducing apparatus as setforth in claim 10,wherein the control means is operative so that whendetection result by the amplitude detecting means indicates thatamplitude of the tracking error signal from the tracking error signalgenerating means is amplitude different from amplitude of a trackingerror signal of either the first recording area or the second recordingarea it moves a scanning point on the optical disc by the optical headin a radial direction of the optical disc.
 13. A recording and/orreproducing apparatus for an optical disc including a first recordingarea where data using physical uneven portions are recorded in advance,a second recording area where grooves are formed, a buffering areaprovided between the first and second recording areas, and a managementarea in which management data for carrying out management of datarecorded in the first and second recording areas is recorded,theapparatus comprising:an optical head for reading out data from theoptical disc; and first control means for controlling movement operationof the optical head on the basis of the management data which has beenread out from the optical head,whereby the first control means isoperative so that when the optical head moves from the first recordingarea to the second recording area of the optical disc the first controlmeans inhibits access to the buffering area of the optical disc, andwhen the optical head moves from the second recording area to the firstrecording area of the optical disc the first control means inhibitsaccess to the buffering area of the optical disc.
 14. A recording and/orreproducing apparatus as set forth in claim 13,wherein the apparatusfurther comprises tracking control means (second control means) forcarrying out tracking control by using a tracking error signal generatedon the basis of an output signal form the optical head, the firstcontrol means being operative to stop, in the buffering area of theoptical disc, operation of the tracking control means on the basis ofthe management data which has been read out from the optical disc.